There are a number of commercial applications that utilize a controlled gas atmosphere enclosure. For example, in the semiconductor industry, gases are injected into an enclosed chamber wherein one of the gases is plasmarized and hits a target on a chamber lid causing the target's materials to deposit on a wafer. Other commercial applications include using controlled gases to cultivate biological cultures in an enclosed chamber, such as an incubator.
A conventional incubator is generally rectangular in shape and has up to five insulated walls (top, bottom, left side, right side, and rear). Each wall may have an inner space defined by the inner and outer surfaces of the insulated wall and the inner spaces can be in communication with each other. An insulated front door together with the insulated walls complete the inner chamber of the incubator and the door is typically mounted on hinges on the front side of one of the side walls. The door allows access into the inner chamber where culture plates are placed or removed from the shelves that are provided therein.
It is desirable to maintain optimal conditions inside the incubator in order to promote the desired growth of the cultures and to document the experiment for repeatability by others. In a conventional incubator, gases such as O2, N2, and CO2 are introduced from their respective primary supply tanks into the chamber depending on the growing conditions desired. Additionally, some incubators can also have a secondary or backup tank in addition to the primary supply tank and both supply tanks are controlled by an incubator tank switcher system. The incubator tank switching system can be manually or automatically set to switch from the primary to the secondary supply tank when the primary tank is low on gas or has other problems. Typically, the user sets the CO2 and O2 setpoints and the appropriate gases are added. N2 can be used to purge excess O2 from the incubator when the O2 level in the chamber is too high for the setpoints.
In some experiments, maintaining a certain gas concentration in the chamber is critical to the experiment's success. For example, in some experiments it can be important to maintain CO2 at 5% throughout the experiment either to confirm a hypothesis or to document the process for repeatability. Various parameters can affect the CO2 concentration (and other gases, such as O2), such as the escape of the gas when the incubator door is open, and high humidity levels in the incubator. Another parameter that can affect the CO2 concentration is the pressure and the volume of the CO2 gas supply tank being too low or empty.
Conventionally, in order to ensure that the CO2 level is maintained in the incubator, the user can monitor the incubator tank switcher system or monitor the gas level (gauge) of the supply tank to see if it is near empty. However, these preventive measures may not work when the user forgets to check the volume level or the gauge on a constant basis. Additionally, conventional incubators can have a “tank out” warning that occurs after the supply tank is completely empty. However, this warning is not useful because corrective measures may not be effective by the time the user is notified and a new tank is connected or switched. Additionally, even if the primary supply tank is switched from the primary to the secondary tank automatically, the secondary tank's “tank out” warning will also occur only after the tank is empty. If the gas concentration of a gas fluctuates vastly, such as when the gas concentration is low due to the gas supply tank being empty, it can destroy the experiment and lead to the destruction of months to years worth of research. Thus, it is important to know when the gas concentration of the supply tank (primary or secondary) is near empty so that the user can be prompted to check the level of the tank and take appropriate actions.
Therefore, there is a need for a notification system to allow a user to know when the gas supply tank is about to be empty so that appropriate measures can be taken for improved culture growth.